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R Lindahl

Publications and source records attributed to R Lindahl.

At least 55 records · Page 3Linked to original sources
PubMed1994

Oxazaphosphorine-specific resistance in human MCF-7 breast carcinoma cell lines expressing transfected rat class 3 aldehyde dehydrogenase.

Overexpression of either class 1 or class 3 aldehyde dehydrogenase (ALDH) has been found in cell lines selected for resistance to the oxazaphosphorine (OAP) alkylating anticancer agent cyclophosphamide (CPA). Direct oxidation of the CPA metabolic intermediate aldophosphamide (ALDO) is catalyzed efficiently in vitro by the class 1 ALDH isozyme, but the involvement of the class 3 isozyme in OAP resistance is problematic since in vitro studies do not show efficient oxidation of ALDO. Cell lines were established that express stably transfected rat class 3 ALDH to model the potential role of this isozyme in OAP resistance. Clonogenic survival assay data indicated that even modest expression of rat class 3 ALDH was associated with resistance (2-4-fold) to the CPA analog mafosfamide and that the fold resistance was directly proportional to the class 3 ALDH activity expressed in clonal transfectants. Pretreatment of the highest activity cell line (3A1-31A) with 75 microM diethylaminobenzaldehyde, an ALDH substrate and inhibitor of benzaldehyde oxidation, effectively reversed the 3.8-fold resistance in this line; drug sensitivity was unaffected by diethylaminobenzaldehyde in the control transfected cell line. The resistance conferred by ALDH to mafosfamide is OAP-specific since the 3A1-31A line is also resistant to 4-hydroperoxycyclophosphamide (2.9-fold) and 4-hydroperoxyifosfamide (3.2-fold) but not to the non-oxazaphosphorine drugs phosphoramide mustard and melphalan, which cannot be detoxified by aldehyde dehydrogenase enzymes.

Aldehyde Dehydrogenase↗
PubMed1994

Structure of the 5' flanking region of class 3 aldehyde dehydrogenase in the rat.

Class 3 aldehyde dehydrogenase (ALDH-3) is induced by exposure to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and during chemical carcinogenesis. These inductions as well as the basal expression of ALDH-3 vary significantly in different organs. In order to identify DNA elements controlling ALDH-3 expression, we have cloned and analyzed approximately 5.5 kb of the 5' flanking region of the ALDH-3 gene. Deletion analysis showed that the 5' flanking region contains at least three functional domains: a strong promoter proximal to the transcription start site, inhibitory regions upstream of the promoter, and TCDD-responsive enhancers. The TCDD-responsive enhancers in the ALDH-3 gene were functionally similar to xenobiotic responsive elements in the cytochrome P450IA1 gene. These results indicate that transcription of the ALDH-3 gene is controlled by cooperation of at least three functional domains.

Aldehyde Dehydrogenase↗
PubMed1994

Role of aldehyde metabolizing enzymes in mediating effects of aldehyde products of lipid peroxidation in liver cells.

It is well established that many types of tumor cells have reduced lipid peroxidation capacity compared to their normal counterparts. Changes in the activity of enzymes metabolizing aldehydes produced by lipid peroxidation have also been reported in a variety of tumor cells. We have investigated the relationship between changes in lipid peroxidation and changes in aldehyde-metabolizing enzymes in normal hepatocytes and two representative rat hepatoma cell lines, McA-RH-7777 and JM2. Compared to hepatocytes, both 7777 and JM2 cells have significantly lower basal and prooxidant-induced levels of lipid peroxidation than normal hepatocytes. Using 4-hydroxynonenal (4-HNE) as substrate, both cell lines also have significantly reduced activities of alcohol dehydrogenase (ADH) and glutathione S-transferase (GST) compared to hepatocytes. JM2 cells have significantly increased aldehyde dehydrogenase (ALDH) and aldehyde reductase (ALRD) activities with 4-HNE. In 7777 cells the ALDH and ALRD activities are not different from hepatocytes. The changes in enzyme activity are inversely correlated with the sensitivity of cells to 4-HNE. JM2 cells, with increased ALDH and ALRD and decreased ADH and GST, are much more resistant to the toxic effects of 4-HNE than 7777 cells. Normal hepatocytes and JM2 cells are approximately equally resistant to 4-HNE even though hepatocytes rely primarily on GST-mediated aldehyde conjugation to metabolize 4-HNE. Coupled with previous results from our laboratories, the overall increased sensitivity of certain hepatoma cells to lipid aldehydes appears due to decreased ability of these hepatoma cells to remove toxic products of lipid peroxidation. Moreover, hepatoma cells with increased levels of aldehyde dehydrogenase and aldehyde reductase appear most like hepatocytes in their ability to metabolize lipid aldehydes.

Aldehyde Dehydrogenase↗
PubMed1994

Molecular medicine: a primer for clinicians--Part VI: Introduction to genetic testing.

Application of the tools of molecular biology to clinical medicine is most apparent than in the development of DNA-based diagnostic and predictive tests. Such tests allow direct examination of the DNA of individuals for the presence or absence of the causative or predisposing molecular defect for a disease or condition. In this and the next two papers, in our series, we will discuss various aspects of genetic testing. We will consider the different types of testing, their current and potential clinical applications and discuss some of the major ethical and legal issues that genetic testing poses.

Alleles↗
PubMed1994

Mammalian aldehyde dehydrogenases: regulation of gene expression.

The mammalian aldehyde dehydrogenases (ALDH) are a family of functionally and structurally related enzymes encoded by multiple genes. Genes representing each major class of mammalian ALDHs, Class 1, 2 and 3, have been cloned and characterized. Functional analysis of the 5' flanking regions of these genes is just beginning, but such studies suggest roles for a diverse set of cis-elements and trans-acting factors in the tissue-specific and ligand-mediated expression of the ALDH genes.

Aldehyde Dehydrogenase↗
PubMed1993

Organization and characterization of the rat class 3 aldehyde dehydrogenase gene.

Expression of class 3 aldehyde dehydrogenase (ALDH-3) is constitutive or inducible, depending on the tissue. ALDH-3 induction occurs both during neoplastic development and after exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In order to study the regulation of ALDH-3 gene expression, ALDH-3 genomic sequences have been obtained from normal rat genomic DNA. Two overlapping genomic fragments (ALDH-UTR-1 and ALDH-NL2) contain the entire ALDH-3 gene along with considerable 5'- and 3'-flanking sequences. The rat ALDH-3 gene spans approximately 9 kilobases in length and consists of eleven exons; ten coding and one 5'-noncoding. The region 5' to exon one contains several putative transcription factor binding elements which may be important in the TCDD inducibility of this gene. These include a xenobiotic response element (XRE), a drug response element (DRE), LAP and Ap1 binding sites, and one Sp1 site. There are considerable differences in organization between the rat and human class 3 ALDH genes. Primer extension and RNase protection analysis indicate that both basal and TCDD-inducible expression of the ALDH-3 gene utilize the same multiple transcription start sites.

Aldehyde Dehydrogenase↗
PubMed1993

Aldehyde dehydrogenases: widespread structural and functional diversity within a shared framework.

Sequences of 16 NAD and/or NADP-linked aldehyde oxidoreductases are aligned, including representative examples of all aldehyde dehydrogenase forms with wide substrate preferences as well as additional types with distinct specificities for certain metabolic aldehyde intermediates, particularly semialdehydes, yielding pairwise identities from 15 to 83%. Eleven of 23 invariant residues are glycine and three are proline, indicating evolutionary restraint against alteration of peptide chain-bending points. Additionally, another 66 positions show high conservation of residue type, mostly hydrophobic residues. Ten of these occur in predicted beta-strands, suggesting important interior-packing interactions. A single invariant cysteine residue is found, further supporting its catalytic role. A previously identified essential glutamic acid residue is conserved in all but methyl malonyl semialdehyde dehydrogenase, which may relate to formation by that enzyme of a CoA ester as a product rather than a free carboxylate species. Earlier, similarity to a GXGXXG segment expected in the NAD-binding site was noted from alignments with fewer sequences. The same region continues to be indicated, although now only the first glycine residue is strictly conserved and the second (usually threonine) is not present at all, suggesting greater variance in coenzyme-binding interactions.

Aldehyde Oxidoreductases↗
PubMed1993

Molecular medicine: a primer for clinicians. Part IV: Cystic fibrosis and the power and limitations of molecular medicine.

Cystic fibrosis (CF) is among the most common genetic diseases in caucasians of Northern European ancestry. The cloning of the gene responsible for cystic fibrosis, the characterization of the product of the gene and identification of mutations occurring in CF patients are excellent examples of the potential clinical utility of molecular medicine. The ethical issues associated with the ability to identify carriers of CF mutations highlight the magnitude of the questions molecular medicine raises.

Cloning, Molecular↗
PubMed1993

Molecular medicine: a primer for clinicians. Part I. Essential concepts of human gene expression.

Molecular medicine refers to the application of the tools of modern molecular biology to the practice of medicine. The impact of molecular medicine will be increasingly felt by the practicing clinician as increased understanding of disease etiology, significantly improved diagnostic methods and patient care techniques designed to affect a cure rather than treat symptoms. This first paper in an on-going series provides a basic review of human gene expression as a framework for understanding how molecular medicine is irreversibly altering how clinicians will practice medicine. Subsequent papers will detail the application of molecular biology's tools to the practice of medicine.

Clinical Medicine↗
PubMed1993

Molecular medicine: a primer for clinicians. Part III: Molecular tools for analyzing human genes.

This is the third paper in our series on how today's practicing clinician is affected by the concepts of molecular medicine. Described are the major tools of molecular biologist, previously used primarily in basic research, that are finding widespread application in the day-to-day practice of medicine. Discussed are Southern and Northern analyses, restriction fragment length polymorphisms, the polymerase chain reaction and in situ hybridization as applied to clinical problems.

Blotting, Northern↗
PubMed1992

Regulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin-inducible expression of aldehyde dehydrogenase in hepatoma cells.

The environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces the expression of a number of genes. The biochemical process of the induction of aldehyde dehydrogenase (ALDH-3) was investigated in rat H4IIE hepatoma cells in culture. The kinetics of ALDH-3-induction exhibited parallel increases in the rate of transcription, mRNA, protein, and enzyme activity, all reaching a plateau at 36-48 h after addition of TCDD. Half maximal and maximal inductions occurred at 0.1 and 1 nM of TCDD, respectively. No significant changes in the half-life of ALDH-3 mRNA (14 h) were observed in the cells exposed to three different concentrations of TCDD. Other inducers of xenobiotic metabolism, such as 3-methylcholanthrene and beta-naphthoflavone, also induced ALDH-3 mRNA to a similar level as TCDD, whereas antioxidants or electrophiles, such as tert-butylhydroquinone and dimethyl fumarate, did not show any induction of ALDH-3 mRNA. To examine the involvement of the aryl hydrocarbon receptor (Ah receptor) in the induction of ALDH-3, mouse variant cell lines defective in cytochrome P450IA1-induction and a parental wild type cell line (Hepa1c1c7) were studied. ALDH-3 mRNA and the transcription of its gene were detected in TCDD-treated wild type cells, but not in the treated and untreated variant cells. These results demonstrate that TCDD induces transcription of the ALDH-3 gene via its binding to the Ah receptor.

Aldehyde Dehydrogenase↗
PubMed1992

Occupational exposure to chromium, copper and arsenic during work with impregnated wood in joinery shops.

CCA-impregnated timber contains copper, chromium and arsenic (CCA), and occupational exposure to wood dust as well as the CCA compounds may occur in work with such timber. Dust from commercially available impregnated wood has been found to contain hexavalent chromium, which is regarded as a carcinogen. Apart from determinations of the total amounts of the CCA compounds, specific determination of hexavalent chromium is therefore essential. Selective methods have been applied for control of the work environment in six joinery shops. The mean exposure to wood dust was found to be below 1 mg m-3. The mean airborne concentration of arsenic around various types of joinery machines was in the range from 0.54 to 3.1 micrograms m-3. No hexavalent chromium was detected in any samples and no increased concentrations of arsenic were found in urine from the workers. The presence of arsenic in the work-room air must be considered for appropriate assessment of the occupational environment in joinery shops.

Air Pollutants, Occupational↗
PubMed1992

Aldehyde dehydrogenases and their role in carcinogenesis.

Aldehydes are highly reactive molecules that may have a variety of effects on biological systems. They can be generated from a virtually limitless number of endogenous and exogenous sources. Although some aldehyde-mediated effects such as vision are beneficial, many effects are deleterious, including cytotoxicity, mutagenicity, and carcinogenicity. A variety of enzymes have evolved to metabolize aldehydes to less reactive forms. Among the most effective pathways for aldehyde metabolism is their oxidation to carboxylic acids by aldehyde dehydrogenases (ALDHs). ALDHs are a family of NADP-dependent enzymes with common structural and functional features that catalyze the oxidation of a broad spectrum of aliphatic and aromatic aldehydes. Based on primary sequence analysis, three major classes of mammalian ALDHs--1, 2, and 3--have been identified. Classes 1 and 3 contain both constitutively expressed and inducible cytosolic forms. Class 2 consists of constitutive mitochondrial enzymes. Each class appears to oxidize a variety of substrates that may be derived either from endogenous sources such as amino acid, biogenic amine, or lipid metabolism or from exogenous sources, including aldehydes derived from xenobiotic metabolism. Changes in ALDH activity have been observed during experimental liver and urinary bladder carcinogenesis and in a number of human tumors, including some liver, colon, and mammary cancers. Changes in ALDH define at least one population of preneoplastic cells having a high probability of progressing to overt neoplasms. The most common change is the appearance of class 3 ALDH dehydrogenase activity in tumors arising in tissues that normally do not express this form. The changes in enzyme activity occur early in tumorigenesis and are the result of permanent changes in ALDH gene expression. This review discusses several aspects of ALDH expression during carcinogenesis. A brief introduction examines the variety of sources of aldehydes. This is followed by a discussion of the mammalian ALDHs. Because the ALDHs are a relatively understudied family of enzymes, this section presents what is currently known about the general structural and functional properties of the enzymes and the interrelationships of the various forms. The remainder of the review discusses various aspects of the ALDHs in relation to tumorigenesis. The expression of ALDH during experimental carcinogenesis and what is known about the molecular mechanisms underlying those changes are discussed. This is followed by an extended discussion of the potential roles for ALDH in tumorigenesis. The role of ALDH in the metabolism of cyclophosphamidelike chemotherapeutic agents is described. This work suggests that modulation of ALDH activity may an important determinant of the effectiveness of certain chemotherapeutic agents.(ABSTRACT TRUNCATED AT 400 WORDS)

Aldehyde Dehydrogenase↗